O’Brien has been an emerging leader at West Lakes for the past three yxjmtzywears since becoming the Club’s first-choice ruckman and then Club Champion in 2020.
The 26-year-old has played 57 AFL games since debuting in 2016 and last year signed a four-year contract extension to remain with Adelaide until at least 2025.
“The addition of both Reilly and Ben to the leadership group reflects the growth of our young team and the exciting direction we are heading in,” Adelaide coach Matthew Nicks said in a statement on Friday.
“Importantly for us, they prioritise others but they also lead by example on game day.”